Electrode for gaseous electrical discharge tubes



27, 1934. c FQRST 1,952,428

ELECTRODE FOR GASEOUS ELECTRICAL DISCHARGE TUBES Filed Aug. 16, 1932WINV wfiw v "fliuiiicd Mar. 27,

UNITED STATES ELECTRODE FOR GASEOUS ELECTRICAL DISCHARGE TUBES Albert C.Forst, Alameda, Calif.

Application August 16, 1932, Serial No. 629,045

3 Claims.

The invention relates to means for effecting a connection between an.electrode and lead in" wire therefor as utilized in combination with agaseous electrical-discharge tube, and more particularly to theconstruction and disposition of the connecting portions of suchelectrodes and lead in wires.

An object of the invention is to provide a connection between anelectrode and "lead in wire for an electrical-discharge tube that willretain the members in contacting relation when subjected to severe heatseven when the members are comprised of metals having widely differentco-eflicients of expansion.

Another object of the invention is to form the cooperating connectingportions of the electrode and lead in wire in such manner, and of suchmaterials, that without the use of extra parts and by simply pressingthe portions together a most effective and permanent interlockingconnection will be afforded both electrically and mechanically under alloperating conditions.

The invention possesses other objects and features of advantage, some ofwhich, with the fore-, going, will be set forth in the followingdescription of the preferred form of the invention which is illustratedin the drawing accompanying and forming and forming part of thespecification. It is to be understood, however, that variations in theshowing made by the said drawing and description may be adopted withinthe scope of the invention as set forth in the claims.

Referring to the drawing:

Figure 1 is a sectional view of an electrode and lead in wire connectedin accordance with my invention and operatively disposed within an endof a gaseous discharge tube.

Figures 2 and 3 are side elevations partially in section of theelectrode and lead in wire respectively before and after the electrodehas been pressed about the wire.

Figures 4 and 5 are plan views of Figures 2 and 3 respectively.

Figure 6 is a side elevation partially in section of a modified form ofmy connection.

Figure 7 is a plan view of Figure 6.

Each of the views represents the members considerably oversize in orderto better illustrate the invention.

As illustrated in the drawing, my invention concerns a connection meansfor joining and retaining in contacting relation an electrode 11 and aconductor 12 therefor commonly termed the "lead in wire. The member 11is mounted with part of the wire 12 within a glass tube 13, the wire 12passing through and sealed within an end 14 of the tube. The members 11and 12 are usually connected before insertion in the tube, and whensealed within the tube form with the latter a unit convenient fordistribution to the trade for use with electrical-discharge tubes suchas employed for illuminated signs and the like. Connection of the unitaforesaid to a tubular glass sign is ordinarily readily effected bymerely joining the glass surrounding the electrode to the end of thesign in a manner sealing theelectrode in the end of the sign tube. Thedisposition of an electrode on each end of the sign tube completes theentire sign assembly.

In rendering a sign tube operable, however, the air between theelectrodes must be substantially entirely withdrawn and replaced with asmall amount of a rarified gas such as argon, neon, helium or the like.After the electrodes have been sealed in the ends of the tube, a pump isconnected to a tubulation provided on the tube for such a connection andthe air drained from between the electrodes; In the electrodesthemselves however are small amounts of entrapped gases which if notwithdrawn during the pumping operation are subsequently liberatedincident to heating of the electrodes such as during operation of thesign, and in mixing with the other gases in the tube deleteriouslyaffects the character of the light emitted. These entrapped gasestherefore must be removed during the pumping operation and their removalis generally effected by energizing the electrodes with a highelectrical potential which in causing a bombardment of electrons thereonsufficiently heats the electrodes to effect a liberation of the gases.In order to insure a substantially complete release of the gasescontained in the electrodes, the latter are heated during the pumping ofthe tube well above their normal operating temperature. In instanceswhere the lead in" wire and the electrode are comprised of differentmetals with unlike coefficients of expansion, this severe heating islikely to affect the strength of the jointure between these members. Thelead in wire being necessarily sealed in the end of the glass tube, isselected of a metal having a coeflicient of expansion most nearlyapproaching that of the glass and is therefore usually formed oftungsten when the tube is comprised of pyrex or other hard glass, and ofa copper clad wire where German lead glass is employed.

Heretofore the connection between the electrode and the lead in wire hascommonly been effected through the use of a stem-like projectionextended from an end of the electrode and provided with a bore in whichan end of the wire is inserted, the retention of the wire in the borebeing brought about by contracting the stem portion sufficient to causea frictional or resilient gripping of the wire between the side walls ofthe bore. This type of connection has been suitable in instances wherethe electrode is formed of copper or iron or other comparatively hardmetal of approximately the same coeflicient of expansion as the lead inwire. These harder metals however are difficult to obtain in a purestate and in a form not containing a relatively large amount of foreignmatter and occluded gases which are likely to be discharged into thetube after the latter has been in operation for sometime. One of thebest metals for use as an electrode appears to be aluminum. This metalnot only may be obtained in a very pure state and free from an excess ofoccluded gases, but also appears to withstand disintegration when usedas an electrode for a longer period of time than the harder metalsaforementioned. Considerable trouble, however, has been experienced inthe use of aluminum electrodes due to the latters relatively highcoefficient of expansion. When joined to a tungsten or a copper-cladlead in wire in the manner effecting merely a frictional or resilientgrip as aforesaid, the aluminum electrode rapidly expands away from agripping position on the end of the wire during the bombarding of theelectrode, with the result that the electrode drops off the end of thewire and renders the apparatus inoperative. In accordance with myinvention however, and as hereinbefore stated, the connection betweenthe electrode and the lead in' wire is so made that the differences inexpansion between the parts will not effect a disconnection of thejointure.

It will be noted that the electrode 11 as here shown comprises acylindrical metal body and is arranged with its current emitting portionconfined to a bore 16 extending longitudinally and inwardly from an end17 of the electrode. The other end 18 of the electrode is reduced indiameter and is provided with an inwardly extending bore 19 preferablyterminating short of the bore 16 and arranged for receiving an end 21 ofthe lead in wire. Adjacent the end 21, the lead in wire is provided withan offset or shoulder portion 22 which is arranged for dispositionwithin the bore 19. When the wire has been inserted in the bore 19, thereduced end of the electrode is compressed around the wire, but sincethe lead in wire is of a harder metal than the aluminum comprising theelectrode, the latter will not merely frictionally engage the wire butthe portion thereof defining the bore 19 will fill in and around theoffset 22 whereby a stop surface will be formed in opposing relation tothe offset 22 to prevent any longitudinally outward displacement of thewire relative to the electrode. The compression is effected in adirection at right angles to the plane in which the portion 22 isoffset, and for this reason this latter portion will be pressedsubstantially in its original, form into the walls of the bore andthereby more effectively prevent a withdrawal movement of the wire fromthe electrode. It will now be clear that instead of the wire andelectrode being held together merely by a frictional or resilient grip,an actual interlocking of the members is provided, and before the wirecan become loosened and pull out of the electrode on expansion of thecompressed walls during the bombarding operation, these side walls wouldneed retreat the full width of the offset, or in other words the lengthof the component of the wire disposed at right angles to the axis of thebore, which would necessitate an expansion far greater than would bepresent even in cases of extreme difference in coefllcients of expansionof the wire and electrode.

A modified form of the lead in" wire is illustrated in Figures 6 and '7of the drawing. As here disclosed, the wire 12 is folded at its end toprovide a loop 23 for insertion into the bore 19. As with the previouslydescribed embodiment, the connection is effected by compressing theelectrode about the wire and thereby impressing the latter into the sidewalls of the bore 19. The material of the electrode, it will be clear,engages over the inner side of the bend or the .connected end 24 of theloop and thus provides for the interlock. which positively prevents awithdrawal movement of the wire even, as with the first connection,under extreme conditions of expansion differences between the wire andelectrode.

While'the connection of my invention has been particularly-designed tojoin an aluminum electrode to a lead in wire of the character described,it will be clear that the same may be advantageously employed with anelectrode of any metal of less hardness than the lead in wire used.

I claim:

1. In a connection of the character described, a cylindrical electrodeprovided with a bore longitudinally and inwardly extending from one endthereof arranged to provide the current emitting portion of saidelectrode, the other end of said electrode being reduced and having abore inwardly extending from said end and terminating in spaced relationto said first named bore, a connector wire for said electrode having acrooked portion disposed within said second named more, said wire beingof a harder metal than that comprising said electrode whereby uponcompressing said reduced end in a direction'transverse to its lengthsaid wire Will be impressed into the'walls of said second bore to definea surface opposing and engaging said crooked portion to resistwithdrawal of the wire from the bore.

2. In a connection of the character described, a cylindrical electrodeprovided with a bore longitudinally and inwardly extending from one endthereof arranged to provide the current emitting portion of saidelectrode, the other end of said electrode being reduced and having abore inwardly extending from said end and terminating in spaced relationto said first named bore, a connector wire for said electrode beingfolded at its end to form a loop and disposed with the connected end ofsaid loop inserted in said second bore, said wire being of a hardermetal than that comprising the electrode whereby upon compressing saidreduced end in a direction substantially at right angles to the plane ofsaid loop said wire will be impressed into the walls of said second borewith portions of said walls disposed between the opposed folds of saidloop to thereby engage and stop movement of said connected end of theloop incident to a withdrawal movement of the wire from the bore.

3. An electrode for neon type tubes, comprising a solid aluminum memberhaving a bore adjacent one end providing electrical contact with theneon or equivalent gas in the tube, the other end of the electrode beingsolid and provided with a relatively small bore, a conductor in saidbore and having an offset portion, the mass of material adjacent saidlast named end being crushed inwardly substantially closing said secondbore about said conductor and offset.

ALBERT C. FORS'I'.

